A Low-Cost Aqueous Lithium-Ion Battery Enabled by Hybrid Aqueous/Nonaqueous Electrolytes

Aqueous lithium-ion batteries are promising in large-scale energy-storage applications due to their high-safety, improved rate capability, and environmental friendliness. However, the application of highly concentrated electrolytes increases the battery cost, while constructing a stable solid–electrolyte interphase (SEI) remains challenging in low-concentration electrolytes due to their unstable thermodynamic properties. Herein, a hybrid aqueous/nonaqueous electrolyte (HANE) with a low salt concentration has been designed to enable a wide electrochemical stability window and in situ formation of a stable SEI. The organic cosolvent molecules not only form hydrophobic layers on the anode surface but also disrupt the hydrogen-bond network of water molecules, thereby suppressing the electrolyte side reactions. Meanwhile, the preferential reduction of LiNO 3 additive triggers the formation of a passivation layer to block the contact between the anode and the electrolyte, thereby facilitating the formation of the SEI layer. Consequently, PTCDA||LiMn 2 O 4 full cells have been developed based on the HANE, which can achieve a high reversible capacity with a high Coulombic efficiency of 99.8% and capacity retention of 81% after 500 cycles. This study could provide insight into developing stable low-concentration aqueous electrolytes for high-performance lithium-ion batteries.